116 Warden & l^edler— On the Nature of the [No. 1, 



lessening the activity of the tubers is due to the very slight solubility of 

 oxalate of lime in that acid. And, lastly, the complete loss of all physio- 

 logical action when the tubers were treated with dilute nitric or hydro- 

 cliloric acid is evidently due to the ready solubility of calcic oxalate in 

 those mineral acids. And these assumptions, as we have already indicated, 

 were fully demonstrated by the microscopic examination of sections of 

 the tubers treated with the reagents we have mentioned. One point, 

 however, remains to be explained. We observed that, on drjang, the tubers 

 lost practically the whole of their physiological activity. Clearly there 

 could have been no loss of oxalate of lime on desiccation, and as a matter 

 of fact we found as many crystals on microscopic examination of dried 

 arum as we had found in the fresh tubers. We explain this apparent 

 anomaly in the following simple manner. In the fresh condition of the 

 tubers, the bundles of crystals of oxalate of lime are cone-shaped, more or 

 less, the sharp points covering a wide area, and forming the base, but, in the 

 drying of the tubers, the needles appear to arrange themselves more or less 

 parallel to one another, and the sharp points thus cover a smaller area. 

 And thus, instead of each crystal acting as a separate source of irritation 

 and penetrating the tissues, the bundles act as a whole. It is well-known 

 that finely chopped hair when given with food will cause death by setting 

 up uncontrollable diarrhoea. The hairs covering the legumes of the 

 Mucuna fruriens (cowage) are described as straight, quadrangular pris- 

 matic, and sharply pointed at the apex, 3 mm, long, and thus easily 

 penetrate the skin, causing intolerable itching, which is greatly 

 increased by washing and rubbing. Cowage, as is well known, has 

 long been used as a vermifuge, under the idea that its prickly setae, 

 which irritate the skin so severely and are so difficult to detach, 

 wound and injure the worms, and either kill them or promote their 

 expulsion.* Apparently with a similar object A. tortuosum is used to 

 kill worms which infest cattle during the rains. Lastly, we have an 

 example of finely divided mineral matter causing local irritation, in the 

 so-called hill diarrhoea at Dhurmsala, which is apparently produced by 

 the use of water containing ver}'' fine scales of mica.f 



The usual symptoms produced by arum when administered to the 

 human subject are great local irritation, swelling of the tongue, convul- 

 sions, dilated pupils, insensibility, and coma. J With these symptoms it 

 might be argued that a mechanical theory for the action of aram would be 

 untenable. It might be conceded that local irritation of the mouth would 

 be produced by arum; but objected that, directly the vegetable entered 



* National Dispensatory. 



t Maciiamara's 8th Eeport on Potable Waters in Bengal, Appendix, p. 44. 



X Woodman and Tidy's Toxicology. 



